Re: [PATCH v3] cpufreq/amd-pstate: Skip auto_sel write when it already matches the mode

[Wentao Guan]

Hi,

>On 10/16/2026 11:21 AM, Wentao Guan wrote:
>> Hi,
>> 
>>> Since commit 9dfd13f80c85 ("cpufreq/amd-pstate: Toggle auto_sel in active
>>> mode on shared memory systems"), shmem_init_perf() programs
>>> AUTONOMOUS_SELECTION_ENABLE unconditionally, including in active mode.
>>>
>>> Platforms that exclusively support autonomous selection report this field
>>> as an Integer of 1, as required by the ACPI specification, instead of as a
>>> register descriptor.  cppc_get_reg_val() reads such a field back
>>> successfully, but cppc_set_reg_val() rejects the write with -EOPNOTSUPP
>>> because the entry is not an ACPI_TYPE_BUFFER.
>>>
>>> shmem_init_perf() propagates that error, so every amd_pstate_epp_cpu_init()
>>> fails, cpufreq_register_driver() ends up with an empty policy list and
>>> returns -ENODEV, and amd-pstate refuses to load at all:
>>>
>>>   amd_pstate: failed to set auto_sel, ret: -95
>>>   amd_pstate: Failed to initialize CPU 0: -95
>>>   ...
>>>   amd_pstate: failed to register with return -19
>>>
>>> Skip the write when the register already holds the value the requested mode
>>> needs.  Active and guided mode are fixed on these platforms, which report
>>> auto_sel as 1, while passive mode still fails to load on a platform that
>>> cannot disable autonomous selection, exactly as it did before the
>>> offending commit.
>>>
>>> Fixes: 9dfd13f80c85 ("cpufreq/amd-pstate: Toggle auto_sel in active mode on shared memory systems")
>>> Cc: stable@xxxxxxxxxxxxxxx
>>> Reviewed-by: K Prateek Nayak <kprateek.nayak@xxxxxxx>
>>> Tested-by: K Prateek Nayak <kprateek.nayak@xxxxxxx>
>>> Tested-by: LFRon <ronforever@xxxxxxxxxxx>
>>> Signed-off-by: Wentao Guan <guanwentao@xxxxxxxxxxxxx>
>>> ---
>>> changelog v3:
>>> Include the K Prateek Nayak reviews to remove that ternary op base on current
>>> condition now have.
>>>
>>> v2 link:
>>> https://lore.kernel.org/stable/c3eb86bd-70a6-4bb2-8eff-b2a3c0817514@xxxxxxx/#R
>>> changelog v2:
>>> Accecpt and tested the K Prateek Nayak reviews.
>>> v1 link:
>>> https://lore.kernel.org/stable/20260918054808.48999-1-guanwentao@xxxxxxxxxxxxx/#R
>>> ---
>>> ---
>>> drivers/cpufreq/amd-pstate.c | 6 ++++--
>>> 1 file changed, 4 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c
>>> index 80d99ba1902c9..2d1f5292d1738 100644
>>> --- a/drivers/cpufreq/amd-pstate.c
>>> +++ b/drivers/cpufreq/amd-pstate.c
>>> @@ -532,8 +532,10 @@ static int shmem_init_perf(struct amd_cpudata *cpudata)
>>>  		return 0;
>>>  	}
>>>
>>> -	ret = cppc_set_auto_sel(cpudata->cpu,
>>> -			(cppc_state == AMD_PSTATE_PASSIVE) ? 0 : 1);
>>> +	if ((cppc_state != AMD_PSTATE_PASSIVE) == auto_sel)
>>> +		return 0;
>>> +
>>> +	ret = cppc_set_auto_sel(cpudata->cpu, !auto_sel);
>>>
>>>  	if (ret)
>>>  		pr_warn("failed to set auto_sel, ret: %d\n", ret);
>>> --
>>> 2.30.2
>> 
>> Ping? Nearly a month passed, anything update?
>
>On a similar issue here
>https://lore.kernel.org/all/851316da-2cfa-4a22-947c-1838532d05cf@xxxxxxx/
>Mario had recently pointed out that this might be a BIOS issue on
>systems that may have MSR interface but running an old BIOS that does
>not advertise the CPUID bit.
Seem same issue.

>
>Could you please share your system details here and check if you are
>running the latest BIOS from your vendor?

Emmm, the user report that dmesg showed running on this laptop:
DMI: METAPHYUNI MetamechBook01/MetamechBook01, BIOS AHP958_V00.01_T015A5ME1 02/22/2024
which vendor not ship new BIOS,
but it is verified in AMD Advantage: https://www.amd.com/en/gaming/laptops/advantage-premium.html ...

He also helped me to test the kernel patch.

BRs
Wentao Guan